Integrated Computational Materials, Process and Product Engineering – IC-MPPE 2022

The principles of conventional residual stress analysis using XRD are explained and their further development to enable the determination of the residual stress depth profile are outlined. The actual investigations are focused on residual stress depth profiling concerning WC-Co hardmetals using X-ray diffraction techniques. Additionally, results for hardmetal samples coated with AlCrTiN layers are also presented. The measurements provide the residual stress depth profile near the substrate-coating interface. Besides, corresponding results from ceramic Si3N4 samples are shown. The grazing incidence X-ray diffraction method (GIXD) is an important tool for the determination of residual stress gradients near the material surface. Due to the relatively low penetration depth of X-rays in materials as investigated here, such methods are restricted to a region of a few microns near the surface. The application of this technique and its innovative modifications to obtain a sin2ψ plot at strictly constant mean penetration depth is presented. The equi-penetration grazing incidence X-ray diffraction (EP-GIXD) variant originates from a sin2ψ approach based on the determination of the lattice plane distances of various selected diffraction peaks at a specific angle of incidence. For each measurement dataset the condition ∂τ/∂ψ = 0 is here fulfilled and corresponds strictly to an individual mean penetration depth τ independent from the tilt angle ψ. The residual stress investigation of substrates near the substrate-coating interface is complicated by absorption effects in the coating layer. Rocking curve measurements i.e. the determination of the diffraction intensity as a function of the sample orientation, enable a quantification of the absorption properties of the coating. Finally, a mathematical formalism covering the transformation from the residual stress depth profile viewed as a function of the mean penetration depth to a profile as a function of the real depth is discussed.